I've been making smoothies for a long time - my advice is just to start throwing random ish in there and you'll find out what you like. To beat boredom, use flavorful add-ins like ginger, cinnamon, etc. Some recent faves...
Tropical: Banana, spinach, frozen pineapple and/or mango
PBJ: Spinach, peanut butter, frozen blueberries, frozen raspberries (also good with strawberries or almond butter)
Ginger Peach: Spinach, frozen peaches, banana, sliced fresh ginger root
Chocolate Cherry: Spinach, frozen cherries, almond butter, cocoa powder, honey